The lithography process for manufacturing a device such as a semiconductor device uses an exposure apparatus which projects a reticle pattern onto a wafer coated with a photosensitive agent (photoresist) through a projection optical system. Such an exposure apparatus comprises a plurality of units, i.e., a projection lens which projects a reticle pattern, a laser unit which generates exposure light, an illumination system unit which guides the exposure light to the projection lens, a reticle stage which holds a mask and moves it to a predetermined position, a wafer stage which holds a wafer coated with a photosensitive agent and moves it to a predetermined position, an alignment unit for precisely aligning a mask pattern and the wafer, a transport system unit for transporting the mask and wafer to respective stages, a control unit for performing centralized control for the above-mentioned units, and the like.
The exposure apparatus further includes a large number of units, i.e., air pipes for air-floating the respective stages, a piping unit for distributing and controlling coolant system pipes for cooling a heating element whose heat amount is large, such as a linear motor for stage driving, a driving circuit which drives a linear motor or the like, a sensor amplifier which amplifies the output of a sensor, a control board, and the like.
When, e.g., a measurement device for alignment such as an off-axis scope is used to align a wafer with the optical axis of a projection optical system, a measurement error may occur due to a slight change in temperature. The position of a stage movable in a plane perpendicular to the optical axis of the projection lens is measured by a laser interferometer using a bar mirror arranged in the stage. Even a slight change in temperature in the measurement optical path of the laser interferometer causes air fluctuations. As a result, the refractive index of the measurement optical path changes to cause a measurement error. Additionally, the projection lens itself deforms due to heat expansion, thereby degrading the image characteristics.
In order to solve the above-mentioned problems, a semiconductor exposure apparatus performs precise temperature control by an air conditioner so as to keep the temperature in the apparatus constant. The electrical components such as the driving circuit, sensor amplifier, and control board are accommodated in a box, or the like, so as not to leak heat generated in them. By flowing temperature adjusted air in the box, heat is not dissipated outside from the box.
However, if a box which accommodates a driving circuit, sensor amplifier, and control board as described above, and pipes for cooling the box are provided in an exposure apparatus, the size of an exposure apparatus increases.
As for the performance of an exposure apparatus, increases in accelerations as well as synchronization accuracy of a reticle stage and a wafer stage have been demanded to increase the throughput. To meet this demand, there has been proposed a mechanism, in which a counter mass, which moves in a direction opposite to the driving direction of a stage so as not to transmit vibrations generated upon stage driving outside the stage, is provided to receive a reaction force generated upon stage driving. Mounting of this mechanism also increases the size of an exposure apparatus.
In consideration of the footprint of an exposure apparatus in a factory, an increase in size of the apparatus is not desirable, and it is thus difficult to ensure a space for placing the above-mentioned box.